I put a 10” greenback in one of my 5E3’s. I had a 12” weber the amp sounded OK but not my best one. I think part of the problem the cabinet is made from Canary wood very dense wood I think that had a lot to do with the sound. With the 10” I’m liking the sound so far. Still haven’t been able to open it wide open. I built another 5E3 with a 12” green back it sounded really good (ply cab) That one I gave to friend for helping me paint the doors in our house. I believe the greenbacks are less efficient that the weber 12”. Next I take to my friends house were we can open it up.